Although radiofrequency catheter ablation (RFCA) is useful in the treatment of idiopathic ventricular tachycardia, especially right ventricular outflow tract tachycardia (RVOTT), some tachycardias remain resistant despite several attempts. This study was focused to search of electrocardiographic characteristics suggestive of successful radiofrequency ablation of idiopathic ventricular tahycardia showing LBBB and inferior axis.

The study subjects were 19 patients (mean age 4415, male 5, female 14) those we tried RFCA under the diagnosis of RVOTVT. The study subjects were grouped into success group (N=14) and failed group (N=5). We analyzed the morphologic characteristics of QRS complex during ventricular tachycardias or ventricular premature beats in both groups.

Acute success was obtained in 14 of 19 patients. For RFCA of RVOTT, pace mapping and/or activation mapping were used to select an ablation site as described previously(1). Activation mapping was possible only for 5 patients. All patients except one patient of success group showed inferior axis of QRS during VT. We didn't find significant difference in QRS axis, QRS morphologies in lead 1 and aVL, and QRS width in lead II and V2 between success (N=14) and failed group (N=5). However, in analysis of morphologic comparison of precordial leads, 12 out of 14 patients in success group showed initial r wave in V1 (p=0.017) and 11 patients had precordial transition >V3 (p=0.038). Whereas, in failed group, 4 patients had precordial transition V3 and only one patient showed precordial transition >V3. Initial r of V1 was seen in one patient and remaining 4 patients showed QS pattern in V1.

Analysis of QRS morphology in V1 and precordial transition site may identify patients with high and low success rate during RFCA of idiopathic RVOTT.